NEW:Wisconsin governor threatens to lay off 1,500 workers if senators don't return home

NEW:Judge rules that demonstrators can no longer sleep inside Capitol building

At least 41 rounds of .22-caliber ammunition have been found outside the Capitol

The state Senate approves a resolution allowing police to detain missing Democrats

(CNN) -- Wisconsin Gov. Scott Walker on Thursday warned 14 absent lawmakers trying to stall his controversial budget bill to return to the state Capitol immediately to vote on the measure, or layoff notices will be sent to 1,500 public employees before the weekend.

"Unfortunately, if we don't have action by tomorrow we have a legal and moral obligation to start forewarning people," Walker said a Thursday night press conference.

The layoffs would take effect April 1, the governor said.

Walker's threat to start laying off workers capped the third week of a high-stakes drama playing out in Wisconsin.

Meanwhile, a Dane County judge on Thursday issued an order barring demonstrators from the state Capitol after business hours. During protests, some demonstrators have been sleeping inside the building. The order from Wisconsin Circuit Court Judge John Albert gave the state Department of Administration the authority to forcibly remove anyone who refuses.

Most of the protesters remaining at the Capitol Thursday evening appeared to abide by the judge's order. Some initially balked at the demand they leave the Capitol by the building's regular 6 p.m. closing time. However, a long line of demonstrators later filed out of the building chanting slogans, carrying bedrolls and banging homemade plastic drums.

Concerns about safety risks arising from the nonstop presence of demonstrators at the Capitol were heightened Thursday with the discovery of 41 rounds of hollow-point rifle ammunition found outside the building.

Police continued their search for more ammunition, and the person to which it belongs, amid a contentious budget showdown over a measure that would -- among other things -- curb the collective bargaining rights of most state workers.

Walker has repeatedly said the collective bargaining provisions of his bill are not negotiable. The governor showed little sign of backing down from that stance Thursday night.

Instead, Walker repeatedly said he was "frustrated" by the intransigence of the 14 Democratic senators trying to stymie the bill by not showing up to vote. He blamed a core group of "extreme" dissenters for standing in the way of compromise.

"What's probably the most frustrating is I keep getting the sense that many of these responsible senators are seeking a pathway home, however some of the more extreme members of that caucus are putting up a barrier to them," Walker said.

Walker refused to name any of the senators he believes are blocking negotiations. The governor said he and Republican House Speaker Jeff Fitzgerald have been trying to negotiate with some Democrats. Walker refused to talk about what "specifics are on the table."

Weeks of demonstrations in protest of Gov. Scott Walker's proposal have drawn massive crowds to the state legislature since mid-February, contributing to $6.5 million in damages and other costs, state Administration Secretary Mike Huebsch said during a hearing Thursday. The hearing examined the question of public access to the building.

Meanwhile, the state Senate approved a resolution that would hold absentee Democratic lawmakers "in contempt of the Senate" should they not return to the Capitol by late afternoon. The missing lawmakers -- who left February 17 -- had still not returned by Thursday night.

The contempt measure allows state law enforcement to detain and return the 14 Senate Democrats to Wisconsin, according to Senate Majority Leader spokesman Andrew Welhouse.

Walker said he would prefer that the absent senators return of their own accord.

"I personally am going to ... try and compel these senators to come back in terms of making an offer," Walker said.

The lawmakers fled to Illinois to prevent a quorum for voting on the state's budget repair bill, which would limit collective bargaining to wages and require public workers, with the exception of police and firefighters, to cover more of their retirement plans and health care premiums.

But whether the contempt measure is constitutional remains unclear. The state Constitution prohibits the arrest of lawmakers while the legislature is in session, except for "treason, felony and breach of the peace."

Whether Wisconsin law enforcement would be permitted jurisdiction in Illinois to detain the missing Democrats is also unclear.

The stalemate has proven increasingly contentious in recent days as Senate lawmakers adopted a resolution on Wednesday that would fine absentee lawmakers $100 every day they remain missing.

A similar resolution passed a day later in Indiana, where House Republicans imposed a $250-a-day fine against AWOL Democrats who -- like their Wisconsin counterparts -- fled to Illinois in protest of a labor bill.

In Wisconsin, Republicans need a single Democrat to cross party lines and rejoin the 33-member legislature to meet the quorum of 20 lawmakers required in a vote on state fiscal matters. Only 17 lawmakers are required for most other issues.

Union leaders have agreed to pay more for benefits, but view restricting bargaining rights as an assault on workers' rights.

Gov. Walker took to the airwaves Wednesday in support of his belt-tightening measure.

"Every day we fail to act on this just adds more and more to the cost," he told reporters, defending the curtailing of collective bargaining as an integral part of fiscal reform.

Wisconsin is confronted with a looming $137 million shortfall at the end of the fiscal year, June 30. The state faces a $3.6 billion budget gap by 2013.